1. Field of the Invention
The present invention generally relates to regulators, and more specifically, to an input-tracking, automatic output-margining method and system. The present invention describes a method and system for controlling voltage margining of a small regulator located on a logic circuit in communication with an external power supply.
2. Description of Background
During manufacturing test routines, computer logic is often run for sustained periods at voltages higher or lower than the nominal. This is done to ensure the robustness of the product, and the procedure is referred to as margining. For most high-current power supply outputs, the voltage is adjusted dynamically through the use of a DAC (digital-to-analog converter) affecting the regulator's precision voltage reference. This DAC is controlled by a microprocessor internal to the power supply, and is issued instructions from an outside source.
On occasion, small regulators may be located on a system logic board, as opposed to within the power supply itself. These small regulators often have limited features, and it may not be possible to have computer control over voltage margining. Traditionally, two methods have been used to control voltage margining on small on-board regulators.
In a first method, an Intel VRM (Voltage Regulator Module) compliant regulator controller is used. These chipsets include a VID (Voltage ID) feature, which is a series of logic-level inputs that act as a DAC input and allow output voltage to be dynamically adjusted according to the applied bit pattern. This topology requires a digital interface to the regulator, which may not be easily available on a logic board external to the power supply. Additionally, margining capability is limited to the discrete voltage step sizes, which are determined by the chipset manufacturer.
In a second method, an external reference may be supplied on small linear or switch-mode regulators. Several resistor dividers may be used to combine an external margining circuit with the external precision reference, allowing for small voltage changes. Often times, the circuit is simply a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) with a series resistor that toggles a margin state either on or off (e.g., allowing a +/−7% change in output voltage) but does not allow fine resolution adjustability. This method is easier to interface to than the first method, and can offer more control over the maximum margin sizes, but does not have much flexibility.
Accordingly, it is desirable to implement a method that allows extensive margining capabilities, allows more granularity within voltage margining capabilities, and improves output voltage accuracy.